Support "SELECT TOP n [PERCENT]... " queries.

Updated the SQL parser to support "SELECT TOP n [PERCENT]... " queries,
matching the Mocrosoft Access SQL language.

Export these queries from databases with mdb-queries.

include/mdbsql.h

@@ -50,6 +50,7 @@ typedef struct MdbSQL
 	long max_rows;
 	char error_msg[1024];
 	int limit;
+	int limit_percent;
 	long row_count;
 } MdbSQL;
 
@@ -103,7 +104,8 @@ void mdb_sql_bind_all(MdbSQL *sql);
 int mdb_sql_fetch_row(MdbSQL *sql, MdbTableDef *table);
 int mdb_sql_add_temp_col(MdbSQL *sql, MdbTableDef *ttable, int col_num, char *name, int col_type, int col_size, int is_fixed);
 void mdb_sql_bind_column(MdbSQL *sql, int colnum, void *varaddr, int *len_ptr);
-int mdb_sql_add_limit(MdbSQL *sql, char *limit);
+int mdb_sql_add_limit(MdbSQL *sql, char *limit, int percent);
+int mdb_sql_get_limit(MdbSQL *sql);
 
 
 int parse_sql(MdbSQL * mdb, const gchar* str);

src/sql/lexer.l

@@ -72,6 +72,8 @@ null		{ return NUL; }
 ">"		{ return GT; }
 like		{ return LIKE; }
 limit		{ return LIMIT; }
+top		{ return TOP; }
+percent		{ return PERCENT; }
 count		{ return COUNT; }
 strptime	{ return STRPTIME; }
 [ \t\r]	;

src/sql/mdbsql.c

@@ -72,6 +72,7 @@ MdbSQL *sql;
 	sql->sarg_stack = NULL;
 	sql->max_rows = -1;
 	sql->limit = -1;
+	sql->limit_percent = 0;
 
 	return sql;
 }
@@ -473,12 +474,23 @@ int mdb_sql_add_column(MdbSQL *sql, char *column_name)
 	sql->num_columns++;
 	return 0;
 }
-int mdb_sql_add_limit(MdbSQL *sql, char *limit)
+int mdb_sql_add_limit(MdbSQL *sql, char *limit, int percent)
 {
 	sql->limit = atoi(limit);
+	sql->limit_percent = percent;
+
+	if (sql->limit_percent && (sql->limit < 0 || sql->limit > 100)) {
+		return 1;
+	}
+
 	return 0;
 }
 
+int mdb_sql_get_limit(MdbSQL *sql)
+{
+	return sql->limit;
+}
+
 int mdb_sql_add_function1(MdbSQL *sql, char *func_name, char *arg1)
 {
 	fprintf(stderr, "calling function %s with %s", func_name, arg1);
@@ -833,6 +845,13 @@ int found = 0;
 
 	sql->cur_table = table;
 	mdb_index_scan_init(mdb, table);
+
+	/* We know how many rows there are, so convert limit percentage
+	 * to an row count */
+	if (sql->limit != -1 && sql->limit_percent) {
+		sql->limit = (int)((double)table->num_rows / 100 * sql->limit);
+		sql->limit_percent = 0;
+	}
 }
 
 void 

src/sql/parser.y

@@ -62,7 +62,7 @@ typedef struct sql_context
 
 %token <name> IDENT NAME PATH STRING NUMBER
 %token SELECT FROM WHERE CONNECT DISCONNECT TO LIST TABLES AND OR NOT LIMIT COUNT STRPTIME
-%token DESCRIBE TABLE
+%token DESCRIBE TABLE TOP PERCENT
 %token LTEQ GTEQ LIKE IS NUL
 
 %type <name> database
@@ -91,7 +91,7 @@ stmt:
 	;
 
 query:
-	SELECT column_list FROM table where_clause limit_clause {
+	SELECT top_clause column_list FROM table where_clause limit_clause {
 	                mdb_sql_select(parser_ctx->mdb);
 		}
 	|	CONNECT TO database { 
@@ -108,6 +108,17 @@ query:
 		}
 	;
 
+top_clause:
+	/* empty */
+	|	TOP NUMBER { mdb_sql_add_limit(parser_ctx->mdb, $2, 0); free($2); }
+	|	TOP NUMBER PERCENT {
+			if (mdb_sql_add_limit(parser_ctx->mdb, $2, 1)) {
+				yyerror(NULL, parser_ctx, "Percent values must be between 0 and 100");
+			}
+			free($2);
+		}
+	;
+
 where_clause:
 	/* empty */
 	| WHERE sarg_list
@@ -115,7 +126,14 @@ where_clause:
 
 limit_clause:
 	/* empty */
-	| LIMIT NUMBER { mdb_sql_add_limit(parser_ctx->mdb, $2); free($2); }
+	| LIMIT NUMBER {
+			if (mdb_sql_get_limit(parser_ctx->mdb) != -1) {
+				yyerror(NULL, parser_ctx, "Can not have TOP and LIMIT clauses");
+			} else {
+				mdb_sql_add_limit(parser_ctx->mdb, $2, 0);
+			}
+			free($2);
+		}
 	;
 
 sarg_list:

src/util/mdb-queries.c

@@ -62,9 +62,11 @@ int main (int argc, char **argv) {
 	
 	//variables for the generation of sql
 	char *sql_tables = (char *) malloc(bind_size);
+	char *sql_predicate = (char *) malloc(bind_size);
 	char *sql_columns = (char *) malloc(bind_size);
 	char *sql_where = (char *) malloc(bind_size);
 	char *sql_sorting = (char *) malloc(bind_size);
+	int flagint;
 	
 	/* see getopt(3) for more information on getopt and this will become clear */
 	while ((opt=getopt(argc, argv, "L1d:"))!=-1) {
@@ -148,8 +150,22 @@ int main (int argc, char **argv) {
 
 				while (mdb_fetch_row(table)) {
 					if(strcmp(query_id,objectid) == 0) {
+						flagint = atoi(flag);
 						//we have a row for our query
 						switch(atoi(attribute)) {
+							case 3:		// predicate
+								if (flagint & 0x30) {
+									strcpy(sql_predicate, " TOP ");
+									strcat(sql_predicate, name1);
+									if (flagint & 0x20) {
+										strcat(sql_predicate, " PERCENT");
+									}
+								} else if (flagint & 0x8) {
+									strcpy(sql_predicate, " DISTINCTROW");
+								} else if (flagint & 0x2) {
+									strcpy(sql_predicate, " DISTINCT");
+								}
+								break;
 							case 5:		// table name
 								if(strcmp(sql_tables,"") == 0) {
 									strcpy(sql_tables,name1);
@@ -193,9 +209,9 @@ int main (int argc, char **argv) {
 				
 				/* print out the sql statement */
 				if(strcmp(sql_where,"") == 0) {
-					fprintf(stdout,"SELECT %s FROM %s %s\n",sql_columns,sql_tables,sql_sorting);
+					fprintf(stdout,"SELECT%s %s FROM %s %s\n",sql_predicate,sql_columns,sql_tables,sql_sorting);
 				} else {
-					fprintf(stdout,"SELECT %s FROM %s WHERE %s %s\n",sql_columns,sql_tables,sql_where,sql_sorting);
+					fprintf(stdout,"SELECT%s %s FROM %s WHERE %s %s\n",sql_predicate,sql_columns,sql_tables,sql_where,sql_sorting);
 				}
 						
 				mdb_free_tabledef(table);